Machines for making and dispensing coffee-based beverages, particularly for the professional sector, such as bars, restaurants, hotels and catering, are currently known.
They comprise substantially a grinder for coffee beans, a boiler, a pump, an assembly for dispensing hot water with which it is possible to associate in a downward region a filter in which the ground coffee is placed and pressed.
Therefore, once the coffee has been ground, it is pressed in the filter basket holder, which in turn is coupled to the dispensing assembly, and then the pump that dispenses the hot water is activated, thus obtaining the infusion.
The resulting coffee can vary in its organoleptic characteristics as a function, for example, of the amount of ground coffee used, of the degree of grinding, of the extent of the pressure used, of the time in which the water is dispensed.
Italian patents no. 1396581 and no. 1396582, both filed on 23 Oct. 2009, relate to a method for controlling the dispensing pressure in a coffee machine in order to produce and dispense coffee-based beverages; patent no. 1396581 comprises a filter unit that is adapted to contain coffee powder, the method comprising:
supplying a preset quantity of water from a hydraulic pump with a flow-rate that corresponds to at least one nominal dispensing pressure value to a hydraulic circuit that has a fluid connection to the hydraulic pump and to the dispensing assembly, the hydraulic pump being actuatable by means of an electronic control device;
detecting at least one water dispensing pressure value by means of a pressure sensor arranged along the hydraulic circuit, and
if the at least one detected value of the dispensing pressure differs from the at least one nominal pressure value, adjusting the flow-rate of the water dispensed by the pump as a function of the at least one detected dispensing pressure value.
Italian Patent no. 1396582 differs in that it includes at least one dispenser which comprises a filter unit adapted to contain coffee powder, the method comprising:
supplying water to a hydraulic circuit that has fluid connection to the at least one dispenser and comprises a valve with adjustable flow-rate adapted to emit variable quantities of water to the at least one dispenser;
emitting from the adjustable flow-rate valve a preset quantity of water that corresponds to at least one nominal dispensing pressure value, the valve with adjustable flow-rate being actuatable by means of an electronic control device that controls the flow-rate of water in output from the valve;
detecting at least one water dispensing pressure value by means of a pressure sensor arranged along the hydraulic circuit, and
if the at least one detected value of the dispensing pressure differs from the at least one nominal pressure value, adjusting the flow-rate of the water emitted by the adjustable flow-rate valve as a function of the at least one detected pressure value.
These solutions are based specifically on control and adjustment of the dispensing pressure.
However, this method suffers the drawback of requiring continuous control and modification of the pressure and a structural complexity that entails the use of expensive components, all this increasing the overall cost of the machine.
Moreover, it is not possible to keep the result in the cup constant because it is subject to a continuously variable choice on the pressure that can be made by the operator.
Patent Application no. WO2012146641 relates to a weighing device for an espresso coffee machine, the device comprising a weighing platform that can be located in the tray region of the espresso coffee machine below a dispensing assembly, a controller connected to the weighing platform, a start/stop button, a timer unit and a display, all of which are connected to a control unit, such that, during the use, the weight of a dispensing and the time required to dispense it are measured by means of the weighing platform and the timer unit, respectively, and the results are shown on a display.
This solution, too, suffers drawbacks, since it is considered insufficient to weigh the ground coffee and determine the water dispensing time in order to obtain an optimum infusion, and moreover the operator must in any case decide, on the basis of the indications that are present on the display, when to interrupt the dispensing of the water.
Moreover, it is still not possible to keep constant the result in the cup.